What if the air we breathe could be purified by pollution-eating concrete? According to a real-world study conducted by researchers at Eindhoven University of Technology in the Netherlands, it can. The researchers tested this concrete on 1,000 square meters of roads and discovered a 25 to 40 percent decrease in oxides of nitrogen over the roads.

The concrete contains titanium dioxide, which acts as an air purifier by removing nitrogen oxides from the air and, with the aid of sunlight, converting them into “harmless nitrates” (according to an article in Treehugger.) The nitrates are then “rinsed away” by the rain. The concrete also breaks down algae and dirt, so it always stays clean.

This bandaid solution seems like a good (albeit, temporary) way to clean up the outdoor air polluted by toxic vehicle emissions; however, a solution for one problem seems to be the cause of another, in this case. Nitrates in water are not entirely harmless. Too much nitrate can be dangerous, especially for babies and pregnant women or nursing mothers. Nitrates are one of the contaminants filtered out by advanced water filters. If the nitrates are collected and “rinsed away” by the rain, there’s a good chance they could end up in our drinking water, in larger doses than are deemed safe.

So, is there a way to get clean air without risking water contamination in the process?